In most of western Europe the rubella vaccine coverage
is high. However, prior to the introduction of the vaccine in Latin America,
rubella susceptibility in women of childbearing age was 10-25%. Forty
one (93%) countries in Latin America have adopted the rubella vaccine
since 2002. The adult immigrant population in Spain constitutes a group
of susceptibles.
In February 2003, the Madrid Community Measles Elimination Plan detected
an increase in rubella notifications in women who had been born in Latin
America. A descriptive study was undertaken to characterise the outbreak.
A confirmed case was a person with fever or rash and a positive IgM serology,
and living in Madrid, between 1 December 2002 and 31 March 2003. The secondary
attack rate (SAR) per household was calculated.
A total of 19 cases of rubella were identified, 15 were confirmed and
4 were probable cases. Fourteen (73.7%) cases were women at childbearing
age. The mean age was 25.1 years. One pregnancy was diagnosed with a voluntary
termination. Eleven (57.9%) cases were from Ecuador. The mean time of
residence in Spain was 41 months. None of the cases or the 54 (78.3%)
household contacts had been vaccinated against rubella. The SAR was 9.1%.
This study showed the spread of rubella in the susceptible Latin American
Community that is resident in Madrid. The interventions proposed were
a vaccination programme towards immigrants, a health education campaign
to prevent congenital rubella, and a health professional training programme
case management.

Introduction

Immunisation strategy

Rubella immunisation was introduced in Spain in 1979, and given to
11 year old girls. In 1981, the measles, mumps and rubella (MMR) vaccine
was included in the national immunisation schedule for children of both
sexes at 15 months of age. In 1995, a booster dose of MMR vaccine was
introduced for both sexes at age 11 to 13 years.

In 1996, results of a serological survey suggested that antibody prevalence
against rubella was higher than 95% [1]. Later, the MMR schedule was
changed, and the booster dose was brought forward to pre-school age
children (3 to 6 years old).

The MMR vaccine is currently part of the childhood immunisation programme,
which includes a first dose at 12-15 months and a booster at 3-6 years.
If a child has not received the second dose of rubella vaccine by the
age of 11-13 years, a booster dose is offered (FIGURE 1).

Since 1985, high vaccine coverage has helped to achieve a dramatic drop
in rubella incidence. In 1999 the annual incidence rate was 1.4 cases
per 100 000 inhabitants. However, higher incidences still exist in some
regions, such as the Canary Islands (10.8/100 000), Ceuta (26/100 000)
and Melilla (54.2/100 000).

Incidence of congenital rubella syndrome

In 1998, there were seven cases of CRS detected in Spain (2 per 100
000 live births).

The Madrid Community serological survey carried out in 2000 indicated
that 95% of all age groups were protected against rubella, and that
98.6% of women of childbearing age (16-45 years old) had protective
antibodies [2]. Nevertheless, CRS cases were declared in Madrid in 1998,
1999 and 2001 [3].
Remaining susceptible individuals are probably the consequence of existing
areas with low vaccine coverage and immunisation failures.

We describe here the latest rubella outbreak in Madrid in 2003, in
which the population affected were unimmunised people living in Spain
who had been born in Latin America.

In February 2003, the surveillance system for measles, within the framework
of the Madrid community measles elimination plan [4], detected an increase
in the notification of cases of rubella. Under the measles elimination
plan protocol, all suspected patients presenting fever and exanthema
must undergo a serologic screening for measles, rubella and parvovirus
B19.

The affected population were mostly women of reproductive age who were
born in Ecuador, Colombia, the Dominican Republic and Argentina.

We conducted a descriptive study to characterise the magnitude of the
outbreak, define the transmission patterns and recommend control measures.

Methods

Applying the European case definition, the cases were classified as
confirmed or probable. A confirmed case of rubella was defined as a
person with rash and fever (more than 38.5ºC), who had been born
in Latin America or was a family member of such a person, with a positive
serology (IgM) confirmed by the regional public health laboratory, and
who was resident or had visited Madrid, between 1 December 2002 and
31 March 2003. A probable case was a person with symptoms of rubella,
and with an epidemiological link to a confirmed case but without laboratory
confirmation.

A contact was defined as a person who was a family member of, working
with, or had a social relationship with a case, and who was a resident
of or visitor to Madrid during the same study period.

The household secondary attack rate (SAR) was defined as the number
of secondary cases occurring in susceptible contacts of an index case
in a family. A susceptible contact was someone with no history of rubella
vaccination, who had not undergone a serologic test. A secondary case
was a case occurring in the 21 days following contact with an index
case.

Results

By active case finding, review of the notifiable disease register and
by interviewing the cases, 19 cases of rubella were identified. Eleven
cases suspected to have measles were found to have rubella by IgM serology.
Three other suspected rubella cases were confirmed by positive IgM serology,
and all 14 cases had low IgG avidity test [5]. Furthermore, during case
finding, a probable case detected in January was confirmed by rubella
IgG serology. The 4 remaining cases were classified as probable. The
19 cases were grouped within twelve household units: fourteen were considered
to be primary cases and five were secondary (FIGURE 2).

Fourteen cases (74%) were in women of childbearing age (mean age 25 years,
range 15 - 38 years). A pregnancy was diagnosed in one of the cases and
a voluntary termination of the pregnancy was carried out. The health districts
most affected were Centre West, South II, Southeast and North: 80% of
the cases were found in these districts. Ecuador was the country of origin
of 11 patients (58%); the other patients had been born in Argentina, Colombia
and the Dominican Republic. The mean time of residence in Spain was 41
months (range 4-132 months). Previous rubella vaccination was not reported
for any of the cases.

In the case-contact study, we identified a total of 93 contacts who
had rubella infection during the period of infectiousness of the 19
rubella cases. Of those, 73 (78%) had not been vaccinated against rubella
and 40 (43%) contacts were women of reproductive age. Overall, 69 contacts
were considered to be household contacts. The SARh was 9.3%.

Discussion

Our study suggests that the Latin American community in Madrid represents
a new group which is susceptible to rubella infection. The resurgence
of rubella infection in the population of people born outside Spain
is a serious public health problem and a drawback to the measles elimination
plan and the rubella control program.

The limitations of the outbreak study were possible misclassification
bias introduced during ascertainment of cases and contacts, when some
asymptomatic cases were considered to be susceptible contacts, and some
immune contacts, due to previous asymptomatic infection, were classified
as susceptible contacts. As a result of these misclassifications, the
household SAR could be an underestimation of the reproductive rate of
the disease. The SAR might have been much higher if all the asymptomatic
cases had been identified, and all the immune contacts excluded.

If we accept a rubella reproductive rate (Ro) of 6 to 16 [6], and 40-50%
of the cases to be asymptomatic, we can estimate that the magnitude
of the outbreak was larger, and that the surveillance system network
only detected a few symptomatic cases. Additionally, as most of the
cases were in women of childbearing age, the surveillance of CRS should
be strengthened.

In the framework of the national health system [7] in Spain, the principle
of universal access to healthcare services ensures that those who migrate
to Spain, whether they reside there legally or illegally, have the right
to the same healthcare as the rest of the population of Spain. Several
regional initiatives have been developed to ensure special healthcare
programmes for migrants. One example is the Plan Integral para la Inmigración
en Andalucía (Andalusia Immigrant Healthcare Programme) [8],
which is developing a healthcare strategy that takes into account the
epidemiological characteristics of the country of origin. In the adult
healthcare programme, it is recommended that all women of childbearing
age be vaccinated against rubella at their first visit to the healthcare
services.

In the 1990s, in Spain as in other western European countries, a new
population phenomenon occurred with the arrival of large numbers of
people from other countries. In Spain, people who were born in Latin
America have tended to settle in the province of Madrid. In 2001 [9],
there were 210 000 Madrid residents who had been born in Latin America,
representing 3% of the total population of Madrid.

To better understand this new public health problem, a serologic surveys
panel, used by the Pan American Health Organization (PAHO) to estimate
rubella susceptibility in women of childbearing age in Latin America
countries, was reviewed prior to the introduction of rubella vaccine.
The rubella susceptibility ranged from 10-25% [10], with large variability
both between and within different countries.

Rubella vaccine has been progressively introduced in Latin America
[11] since 1998. In 2002, 41 (93%) of the 44 countries and territories
in the Americas Region had included MMR or measles-rubella (MR) vaccine
in their childhood immunisation programmes. The remaining three countries,
the Dominican Republic, Haiti, and Peru, plan to follow in 2003-2004
[12].

With reference to the previous information we can assume that a large
proportion of the Latin American born adults in Madrid were not protected
against rubella infection by natural or vaccine induced immunity.

Conclusion

We detected the spread of rubella infection in the susceptible Latin
American community in Madrid. A large proportion of this community are
women whose fetuses are at high risk of developing CRS if infected during
pregnancy
(FIGURE 3).

The measles elimination plan surveillance system was able to detect the
occurrence of suspected cases of rash and fever in adults, which by differential
diagnosis were found to be rubella infections.

In response to this emerging situation, the interventions proposed
to prevent new outbreaks are the development of a combined immunisation
programme aimed at the community of Latin American born people resident
in Spain. The strategy rests on the creation of an adult immunisation
programme, together with the MMR vaccine schedule in the childhood immunisation
programme.

Additionally, as part of the CRS prevention strategy, all women of
childbearing age who were born in Latin America should undergo rubella
serology at their first visit to healthcare services. Women found to
be susceptible to rubella infection should be systematically vaccinated.

These intervention activities should be carried out alongside a health
education campaign to mobilise the participation of the Latin American
community, through their associative organisations, such as the immigrant
forum, NGOs, churches and sport clubs. Healthcare professionals should
be trained in the measles elimination and rubella control protocol.

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